The script file

The second section of the buildfile starts with the [+script]
attribute — this tells mkifs that the
specified file is a script file, a sequence of
commands that you want
procnto
to execute when it's completed its own startup.

Note:
Script files look just like regular shell scripts, except
that:

special modifiers can be placed before
the actual commands to run

some commands are builtin

the script file's contents are parsed by mkifs before
being placed into the image

In order to run a command, its executable must be available
when the script is executed. You can add the executable to
the image or get it from a filesystem that's started before
the executable is required. The latter approach results in a
smaller image.

In this case, the script file is an inline file
(again indicated by the open brace). The file (which
happens to be called ".script")
contains the following:

This script file begins by creating a symbolic link to
../../proc/boot/libc.so.3 called
/usr/lib/ldqnx.so.2.

Next the script starts a serial driver
(the fictional devc-ser8250-abc123)
in edited mode with hardware flow control disabled
at a baud rate of 115200 bps at a particular physical memory address.
The script
then does a reopen to redirect standard input, output, and error.
The last line simply displays a message.

As mentioned above, the bootstrap file can set the _CS_PATH
and _CS_LIBPATH configuration strings.
You can set PATH, LD_LIBRARY_PATH, and other
environment variables if the programs in your script need them.

Note:
Startup scripts support foreground and background processes.
Just as in the shell, specify an ampersand (&) on the
command line to make the program run in the background.
If you run a program in the foreground, and it doesn't exit, then
the rest of the script is never executed, and
the system might not become fully operational.